Nowadays, use of mobile phones has become more and more widespread, and almost every person has a mobile phone. On the other hand, hand-free telephones have also become widely used, so it is often the case that both a hand-free telephone and a mobile phone are available for communication in some places. To meet many people's demands, a call forwarding function is defined in mobile phones. However, a user who has enabled the call forwarding function might forget to cancel the call forwarding function later for some reasons, and this will cause a loss to the user due to missing of the call.
Accordingly, there is still room for improvement and development of the prior art.